Efforts have been made to minimize cervical spine injuries to football players, motorcyclists, and others who may be involved in collisions, related impacts or blows. In the past, hyperflexion and hyperextension injuries to the neck were considered to be the primary mechanisms responsible for severe cervical spine trauma. Many types of neck rolls or collars, both foam and inflatable, have been tried, as have check straps, to limit flexion and extension of the cervical spine. Thus, for example the U.S. patent to Ettinger, 3,855,631, Dec. 24, 1974, discloses an inflatable protective neck collar for a football player. The collar is a separate element but is constantly inflated after being put on to fill the gap between the head and shoulders, thus inhibiting free movement of the head. Further, the collar is inflated only to the extent that normal head and neck movements allegedly are unimpeded. Accordingly, severe impact forces to the crown of the helmet still are transmitted to the cervical spine.
Similar inflatable neck collars have been designed for motorcyclists which normally are deflated but inflate automatically on a collision. See, for example, European patent 0,043,990, published Jan. 20, 1982, and German patent 2,717,712, Oct. 26, 1978. In both, however, the collars are not inflated automatically on impact on the crown of the helmet but instead on collision of the motorcycle. Still further, the impact sensor, gas generator, igniter and battery are not carried by the helmet. Additionally, neither patent discloses a construction which will specifically protect the wearer against serious cervical spine injuries on an impact to the crown of the helmet.
There also has been devised in U.S. Pat. No. 3,134,106 to Shaffer et al, dated May 26, 1964, a protective football helmet arrangement wherein the helmet is rigidly fixed to the shoulder pads so as to allow absolutely no motion of the helmet relative to the shoulders, but the head is free to turn therein, however, this arrangement is highly impractical and is not in use.
German Laid-Open Patent Application 3,142,962 to Seeger et al. describes a motorcycle helmet having an inflatable bag on its lower rim and a mechanism for inflating the bag when acceleration sensors detect a sudden change in acceleration of the wearer, e.g., in a collision. This helmet is designed to prevent injuries caused by lateral and twisting forces resulting from the rider's inertia and the sudden stop of the motorcycle. The horseshoe shape of the inflatable bag in the Seeger et al. device will not prevent injuries resulting from axial compressive forces such as those that occur in football games. Moreover, studies have shown that injuries of this type occur within approximately 30 milliseconds of impact, and the 300 to 500 millisecond reaction time of the Seeger et al. helmet would therefore be ineffective for this purpose.
All of the above efforts have attempted primarily to limit flexion and extension of the spine and also, to some extent, axial compression. However, they did not allow full cervical range of motion and provide instantaneous cervical support when required.
There have been tremendous advances in helmet design and shoulder pad function recently. Helmets now are of variable density polycarbonate shells with pneumatic webs that are inflatable to fit a player's head. Face guards are well-designed to give clear and unobstructed vision and prevent finger-to-face contact. Shoulder pads are equally well engineered to avoid shoulder and clavicle injuries on impact. The weakest link, the cervical spine, has had little (if any) protection. The only preventive measures to date have been education to coaches and players, avoidance of "spearing", i.e., using the head as a battering ram to butt an opponent, and strengthening of the neck muscles and the cervical spine. In reality, however, there is no currently available device to instantaneously stabilize the cervical spine on axial impact.
The mechanism of the typical cervical spine injury in football is as follows. A player flexes his head to spear an opponent, the helmet stops and the trunk compresses the fragile cervical spine like an accordion. Initially, the disks are compressed, followed by the bony vertebrae. The cervical nerve roots are compressed and the player feels "burners" or "stingers" in his arms. If compressed further, the spine flexes and then fractures, subluxes or dislocates.
The most catastrophic head and neck injuries in tackle football are quadriplegia and death. Detailed analysis has determined that most of such serious cervical spine injuries in tackle football have been caused by axial loading, i.e., impact directly on the crown of the helmet. This occurs in "spearing". See "Prevention of Cervical Spine Injuries In Football" in the periodical "The Physician And Sportsmedicine", Vol. 19, No. 10, October, 1991.